Use CRL Self Tapping Tek Screws with the installation of 100, 200, 300, and 350 Series Railings. These Tek Screws are stainless steel #8 x 3/4 inch (19 millimeter), and have special crosscuts which allow them to tap their own threads in aluminum. Screws require an 1/8 inch (3 millimeter) size Square Insert Bit to install.